feat(flutter): 增加目录加载诊断与前台重试

test/discover/home_all_dramas_grid_test.dart

@@ -135,6 +135,9 @@ void main() {
 
     expect(find.byKey(const Key('home-categories-error')), findsOneWidget);
     expect(find.text('Retry'), findsOneWidget);
+    expect(find.byKey(const Key('catalog-debug-endpoint')), findsOneWidget);
+    expect(find.byKey(const Key('catalog-debug-error')), findsOneWidget);
+    expect(find.textContaining('discover feed unavailable'), findsOneWidget);
   });
 
   testWidgets('should_show_search_results_when_text_changes', (tester) async {

test/home/catalog_diagnostics_test.dart

@@ -0,0 +1,60 @@
+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:fruitshorts/core/config/app_config.dart';
+import 'package:fruitshorts/core/data/services/catalog_retry.dart';
+import 'package:fruitshorts/core/theme/app_colors.dart';
+import 'package:fruitshorts/l10n/app_localizations.dart';
+import 'package:fruitshorts/pages/home/home_view.dart';
+
+void main() {
+  tearDown(AppConfig.clearRuntimeBaseUrl);
+
+  testWidgets('should_show_endpoint_and_raw_error_in_debug_failure', (
+    tester,
+  ) async {
+    AppConfig.applyRuntimeBaseUrl('http://probe.test:8081');
+    await tester.pumpWidget(
+      MaterialApp(
+        locale: const Locale('en'),
+        supportedLocales: AppLocalizations.supportedLocales,
+        localizationsDelegates: AppLocalizations.localizationsDelegates,
+        home: Scaffold(
+          body: HomeFailureView(
+            error: 'SocketException: Connection refused',
+            onRetry: () {},
+          ),
+        ),
+      ),
+    );
+
+    final endpoint = tester.widget<Text>(
+      find.byKey(const Key('catalog-debug-endpoint')),
+    );
+    expect(endpoint.data, '服务地址：http://probe.test:8081');
+    expect(endpoint.style?.fontSize, 12);
+    expect(endpoint.style?.color, AppColors.subtle);
+    expect(endpoint.maxLines, 2);
+
+    final error = tester.widget<Text>(
+      find.byKey(const Key('catalog-debug-error')),
+    );
+    expect(error.data, '错误：SocketException: Connection refused');
+    expect(error.style?.fontSize, 12);
+    expect(error.style?.color, AppColors.subtle);
+    expect(error.maxLines, 2);
+  });
+
+  test('should_probe_before_reloading_catalog', () async {
+    final steps = <String>[];
+
+    await retryCatalogLoad(
+      probe: () async => steps.add('probe'),
+      reload: () async => steps.add('load'),
+    );
+
+    expect(steps, ['probe', 'load']);
+  });
+}